Throng

Throng decorators enable caching & throttling of class methods in your app.

meaning: a large, densely packed crowd of people or animals. "he pushed his way through the throng"

An unintrusive approach for cache and throttle, that can be applied any where in a typescript application.

Install

npm i @methodus/throng

Usage

import {Cache, Throttle} from '@methodus/throng';

export class TestClass{

    @Cache(120, 2) // 120 is the cache TTL, 2 is the number of concurrent executions for the expire rerun
    public async cacheMethod(key1:string, key2:string: ){
        /// function code
        return;
    }

    @Throttle(3) // 3 in the number of concurrent operations
    public async throttledMethod(){
        /// function code
        return;
    }

    @Cache(120) // 120 is the cache TTL
    @Throttle(3) // 3 in the number of concurrent operations
    public async combinedMethod(){
        /// function code
        return;
    }

}

@Cache( ttlTime: number, 
       reloadThrottleLimit: number,
       keyLength?: number | Function, 
       setCacheFunction?: Function,
       filterCacheFunction?: Function )

ttlTime

Time in seconds until records expire.

reloadThrottleLimit

A number value or a function returning it for the amount of concurrent executions when refreshing the cache record.

keyLength

A number value or a function returning a string key to be used as the cache item key. If a number is returned it will be used as the amount of arguments to take from the function args for the creation of the key hash.

setCacheFunction

the return value of the function will be stored in the cache, if false is returned nothing will be stored in cache.

@Cache(120, 2, ,2 , (data)=>{ return somenewData }) 
    public async cacheMethod(key1:string, key2:string: ){
        /// function code
        return;
    }

filterCacheFunction

This function will be called before the cache item check, if it return false, the entire cache operation will be skipped (no-cache)

@Cache(120, 2, 2 ,null,  (args)=>{ return args[2] // arg2 is the 3 argument of the decorated function }) 
    public async cacheMethod(key1:string, key2:string, useCache: boolean ){
        /// function code
        return;
    }

@Throttle( limit: number)

limit

Time limit for concurrent execution of the method.

Global throttle limit

By default Throttle uses a global limit object, if you wish to have seperated queues disable the default by passing: THROTTLE_GLOBALLY with the value false

Debug

set "DEBUG" env variable to:

methodus:throng:*
methodus:throng:cache
methodus:throng:throttle

Env Options

CACHE_CHECK_PERIOD:number - the interval for cache expiry check.

CACHE_DELETE_ON_EXPIRE=true: boolean-string - whether to delete the objects as they expire.

CACHE_RELOAD_ON_EXPIRE=false: boolean-string - whether to execute the original function at the end of TTL.

CACHE_USE_CLONES=true: boolean-string - whether to use the original objects in the cache collection or make copies.

THROTTLE_GLOBALLY=true: boolean-string - use a global limit for all decorated methods (throttle);

boolean-string means 'true' | 'false'

Disable

pass THRONG_OFF to completly disable